This invention relates to the synthesis of an aliphatic 1,3-diol, particularly 1,3-propanediol, from ethylene oxide and syngas in one step. More particularly this invention relates to a catalyst that provides good yields under mild conditions in the one-step synthesis of 1,3-propanediol and demonstrates advantages with respect to cost and performance. The catalyst of the invention comprises a homogeneous bimetallic cobalt-ruthenium catalyst in combination with a class of bis(phospholano)alkane ligands, solubilized in an ether solvent.
Aliphatic 1,3-diols, particularly 1,3-propanediol, have many applications as monomer units for polyester and polyurethane, and as starting materials for the synthesis of cyclic compounds. For example, CORTERRA(copyright) polymer is a polyester characterized by outstanding properties that is made of 1,3-propanediol (hereafter 1,3-PDO) and terephthalic acid. There is much interest in the art in finding new routes for synthesizing 1,3-PDO that are efficient, economical, and demonstrate process advantages.
U.S. Pat. Nos. 3,463,819 and 3,456,017 teach the hydroformylation of ethylene oxide to produce 1,3-propanediol and 3-hydroxypropanal (hereafter 3-HPA) using a tertiary phosphine-modified cobalt carbonyl catalyst.
U.S. Pat. No. 5,304,691, assigned to Shell, discloses a method of hydroformylating ethylene oxide to 3-hydroxypropanal and 1,3-propanediol in a single step using an improved catalyst system comprising a cobalt-tertiary phosphine ligand in combination with a ruthenium catalyst. In ""691, 1,3-PDO and 3-HPA are produced by intimately contacting an oxirane, particularly ethylene oxide (hereafter EO), a ditertiary phosphine-modified cobalt carbonyl catalyst, a ruthenium catalyst promoter, and syngas (carbon monoxide and hydrogen) in an inert reaction solvent at hydroformylation reaction conditions. A PDO yield of up to 86-87 mole % is reported, using a catalyst comprising cobalt ligated with 1,2-bis(9-phosphabicyclononyl)ethane as bidentate ligand, and either triruthenium(0) dodecacarbonyl or bis[ruthenium tricarbonyl dichloride] as cocatalyst. Also see U.S. Pat. No. 5,304,686 which discloses the synthesis of 3-hydroxypropanal using a ditertiary phospine-modified cobalt carbonyl catalyst and a catalyst promoter.
The production of 1,3-PDO in one step with minimal impurities and byproducts involves recycle and requires a catalyst system with good stability both during 1,3-PDO synthesis and during product recovery and recycle. It is desirable in the art to identify alternative catalyst systems that demonstrate potential advantages in the one-step production of 1,3-PDO.
In accordance with the foregoing, the present invention provides a new class of ligands for use in a hydroformylation/hydrogenation catalyst composition. The ligands of the present invention provide potential advantages with respect to cost and performance. The invention is a catalyst complex comprising:
a) A cobalt component consisting essentially of one or more non-ligated cobalt compounds; and
b) A ruthenium component comprising in major part a ruthenium carbonyl compound ligated to a phospholanoalkane ligand.
The novel oxirane hydroformylation catalyst of the present invention involves a complex that is postulated to be a cobalt-ruthenium-phospholanoalkane complex. One characterizing feature of the new catalyst is the use of a phospholanoalkane ligand ligated to ruthenium rather than cobalt, as is the case in U.S. Pat. No. 5,304,691. A number of phospholanoalkane ligands are effective, particularly bidentate, bis(phospholano)alkanes.
The invention also provides a one step process for preparing a 1,3-diol, comprising the reaction of an oxirane with syngas at hydroformylation conditions in an inert solvent in the presence of the catalyst complex of this invention.